Maggie Gavin Garrity (born Peggy Sue Gavin) is a fictional character on the FX drama Rescue Me. The character is played by Tatum O'Neal.

Maggie is Tommy and Johnny Gavin's younger sister, who returns to her old neighborhood after she finds out that their father, Michael, is supposed to inherit money from his recently deceased wife. She is the black sheep of the family, who resent her for turning her back on them; meanwhile, she resents them just as much, engaging in self-destructive behavior just to hurt them. She begins relationship with Sean Garrity, a member of Tommy's fire crew, but secretly dated four other men behind Sean's back. When Sean finds out and confronts her about it, his assertiveness leads to her dropping her other lovers for Sean. The two get engaged, though the relationship falls apart when Sean realizes that he could not physically handle being married to her. Maggie and Sean get back together during Johnny's funeral, and pays the priest $500 to marry them in the cemetery. Later throughout the fourth season, she divorces Sean. Throughout the rest of the series, Maggie starts going to AA meetings and achieves sobriety. In the series finale, Maggie attends Lou's funeral and makes a passionate speech thanking him for always treated her with kindness.